Atom Probe Tomography Using an Extreme Ultraviolet Trigger Pulse
Benjamin Caplins, Ann Chiaramonti Debay, Jacob Garcia, Norman A. Sanford, Luis Miaja Avila
Atom probe tomography (APT) is a powerful materials characterization technique capable of measuring the isotopically resolved three-dimensional (3D) structure of nanoscale specimens with atomic resolution. Modern APT instrumentation most often uses an optical pulse to trigger field ion evaporation -- most commonly, the second or third harmonic of a Nd laser is utilized (\emphca.} 532 nm or 355 nm). Herein, we describe an APT instrument that utilizes ultrafast extreme ultraviolet (EUV) optical pulses to trigger field ion emission. The EUV light is generated via a commercially available high harmonic generation (HHG) system based on a noble gas filled hollow core fiber. The centroid of the EUV spectrum is tunable from around 25 eV to 45 eV dependent on the identity of the gas in the fiber (Xe, Kr, or Ar). EUV pulses are delivered to the APT analysis chamber via a vacuum beamline that was optimized to maximize photon flux at the APT specimen apex while minimizing complexity. We describe the design of the beamline in detail including the various tradeoffs involved. We characterize the spectrum of the EUV light and its evolution as it propagates through the various optical elements. The EUV focus spot size is measured at the APT specimen plane and the effects of misalignment are simulated and discussed. Long-term stability of the EUV source is demonstrated over more than a year. Finally, APT mass spectra are shown demonstrating the instrument's ability to successfully trigger field ion emission from semiconductor (Si, GaN) and insulating materials (Al$_2$O$_3$).
, Chiaramonti Debay, A.
, Garcia, J.
, Sanford, N.
and Miaja Avila, L.
Atom Probe Tomography Using an Extreme Ultraviolet Trigger Pulse, Review of Scientific Instruments, [online], https://doi.org/10.1063/5.0160797, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936900
(Accessed December 8, 2023)